A locomotive consist is the arrangement of locomotives, slugs, and power tenders which are coupled together to provide motive power to a train. In one known arrangement, multiple independent locomotives are linked together using multiple-unit (“MU”) controls and operated as a single unit. Locomotives traditionally used in MU arrangements are powered by diesel-electric power sources, where a diesel engine drives a generator to produce electric power. The electricity produced by these engine-generator sets is in turn used to power one or more electric traction motors. The traction motors turn the drive wheels of the locomotive.
The locomotive controllers provided on traditional locomotives, referred to herein as “legacy locomotive controllers”, recognize and control fixed engine-generator combination(s) installed on the locomotive chassis. This arrangement of locomotives has an independent legacy locomotive controller for each locomotive chassis, and shares throttle setting (an input to a locomotive controller), brake settings, and fault indications, which are communicated using a combination electrical and pneumatic connection. Each legacy locomotive controller manages a static, predefined arrangement of one or more engine/generator sets that provide power to the bus, and the generation of tractive effort by traction motors that use the provided electricity. These locomotive controllers also manage fuel use and efficiency, emissions production, and other aspects of the locomotive operation. MU controls relay throttle and brake instructions from a first locomotive (master or “A” units) to one or more second locomotives (slaves or “B” units), where these instructions are independently interpreted by the respective locomotive controller and tractive effort is provided independently by each locomotive of a consist. MU locomotives operate independently and do not share power or engine control signals, nor do they permit a first locomotive controller to make requests of a second locomotive controller. Similarly, legacy locomotive controllers of locomotives operating in MU fashion do not share operational data and do not make operational decisions about the operations of a first locomotive controller based upon the operational characteristics of the second locomotive controller.
Legacy locomotives comprise those locomotives which do not have a locomotive controller that is able to manage multiple simultaneous power generation sources. Legacy locomotives which support multiple simultaneous power generation sources are called “genset” locomotives, as described above.
FIG. 1 is a block schematic diagram illustrating a typical legacy DC locomotive system 10. The DC locomotive system 10 includes two control loops: an engine control loop 12 and an electrical-power control loop 14. These control loops are implemented by legacy locomotive controller 16. A legacy locomotive controller 16 is an analog electro-mechanical assembly, a digital microcontroller-based control system that implements these control loops, or a combination of these technologies. A throttle or “Notch” setting or notch request 18 is set by the operator and is an input to the legacy locomotive controller 16. In the engine control loop 12, the Notch setting 18 is an encoded request for a particular locomotive power setting and is used by the legacy locomotive controller 16 to calculate a set-point for engine speed. The engine control loop 12, implemented by the legacy locomotive controller 16, is responsible for tracking and managing that speed. The electrical control loop 14 of legacy locomotive controller 16 uses the Notch setting 18 to determine a power set-point. The legacy locomotive controller 16 then manages the electrical output power of the engine/generator combination to that power set-point. Collectively, these systems are called “legacy locomotive control systems”.
The high-level schematic diagram for a typical AC locomotive is very similar to that shown in FIG. 1 with the exception that instead of the DC bus wiring directly to DC motors, the power source for the AC induction motors is controlled by a separate AC controller. The AC controller is responsible for distributing power (and reducing it during knockdowns). In an AC locomotive, the DC bus voltage is stored on capacitors which ensure stable power while the AC induction inverters switch the power to the wheels. Thus, for an AC locomotive, the power control portion is similar to that of a DC locomotive.
Legacy locomotive controllers can be generally characterized as outputting engine control voltages (e.g., RPM and generator excitement voltages), receiving sensor input of operational information (e.g., sensor readings indicating actual engine RPM, some fault information, and, in some cases, power bus sensor readings), and then acting to adjust the operation of the engine by varying its control voltages. In locomotives that include multiple engine-generator sets, the legacy locomotive controller manages the locomotives engines and provides power blending by controlling the amount of power and voltage provided by each engine to the common power bus, which permits the provided power to be combined on the power bus.
Legacy locomotive controllers are constructed with a basic assumption that the power sources that they control are provided in a fixed arrangement. If a legacy locomotive controller is unaware of multiple possible power sources, then the use of an external power tender can only be provided on an “all or nothing” basis, where the power tender directly substitutes for the engine-generator on the locomotive chassis. Given the complex nature of locomotive control and the interrelatedness of locomotive loads such as traction motors and blowers, a locomotive's controller, its engine-generator, and an external power tender cannot “share” the generation requirement, with a portion of the power coming from the engine-generator, and remainder of the power coming from the external power tender without the legacy locomotive controller being aware of the power tender and the amount of power it produces. As just one example, the heat generated by the locomotive's electric traction motor must be continuously rejected from the motor apparatus to prevent motor damage and catastrophic failure including fires in the worst cases. In order to reject this heat from the traction motors, locomotives use forced air blower systems to pass air through the internal structure of each traction motor. The power to turn the traction motor blowers comes from the locomotive diesel engine in either mechanical or electrical form. In both instances, the drive speed of the motor blowers is related to the operating speed or power output of the locomotive and adjusting the locomotive diesel engine to compensate for power provided from external sources will reduce the cooling of the traction motors without reducing their actual load (and heat generation).
If the legacy locomotive controller is not programmed to be aware of an additional power source programmed to deliver power to the bus, the legacy locomotive controller will recognize the additional power available on the locomotives power bus and either fault, mis-control one or more power sources or loads, or even turn off the locomotive's engine-generator. In addition, the addition of unexpected auxiliary power sources may result in improper control of other locomotive systems tied to the locomotive engine-generator or to the amount of power being used by locomotives loads (e.g., blowers, auxiliary power), thereby resulting in a non-functioning locomotive.
While some legacy locomotive controllers have been configured to control static arrangements of dissimilar power sources (such as an engine-generator, fuel cell, gas turbine, or batteries) in an effort to reduce emissions and fuel costs, extend locomotive limits, and improve the efficiency of locomotive power, these static arrangements have failed due to the lack of operational flexibility required for day-to-day operation of locomotives and/or operational limitations (such as locomotive range, power production limitations, and requiring support for multiple fuel sources).
Further, the legacy locomotive controllers of existing diesel engines are configured with built-in assumptions regarding the power curve and engine settings (e.g., RPM, generator excitement) that are used to produce specific power/voltages. These operating assumptions are violated by physical limitations induced by separating the power tender from the locomotive chassis (as described above), and by logical considerations that power tenders may have different operating parameters and settings (e.g., differing engine type, characteristics, fuels). In current configurations, power tenders and locomotive controllers must be operated as a single, non-varying consist because of inherent limitations in the locomotive control and the lack of locomotive controller knowledge of differing power tenders and each power tenders instructions and operational characteristics. The lack of flexibility of these older control systems prohibits the use of newer, more desirable, power sources capable of operating with alternative fuel sources and limits operational flexibility made available by swapping out of service units (which takes an entire locomotive/power tender combination out of service).
Newer locomotive power control systems have evolved from electro-mechanical to digital controls offering a variety of new options for power control that perform the same functions as the older electro-mechanical control systems, as well as add new power management and train control functions in order to improve performance and fuel efficiency. However, the cost and technical integration challenges of retrofitting these digital controllers to pre-existing (legacy) locomotives is problematic and are often prohibitive. Generally, this retrofit requires the wholesale replacement of the locomotive control system and some of the locomotive control circuits, as well as substantial modifications to the locomotive engine, generator, and other electrical components on the locomotive. Furthermore, these types of changes typically cause a reclassification of the locomotive and require recertification of the locomotive power plant for safety and emissions. The recertification process requires that the engine emissions be updated to current EPA requirements, which adds additional cost. Combined, these costs are prohibitive.
In light of the above, it would be advantageous to maintain the ability to operate an existing locomotive engine using the fuel for which it was originally designed while adding the ability provide extra power to that locomotive from an auxiliary power source.
It would further be desirable to design an apparatus and method for providing an auxiliary power source for a locomotive that can be integrated with existing electro-mechanical locomotive controls to provide the benefits of being able to incorporate power from alternative fuel sources without replacing or reprogramming the pre-existing locomotive controller.
It would also be desirable to design an apparatus and method that effects proper control of locomotive systems tied to the locomotive engine-generator, such as traction motors and traction blower motors, when an auxiliary power source is used to deliver power to the locomotive power bus.